Precipitation hardening stainless steel alloy



United States Patent M 3,352,666 PRECKPITATIQN HARDENING STAINLESS STEEL ALLOY George H. Foster, Westfield, and Lawrence Mattek, East Brunswick, N.J., and William W. McCandless, Newtown, Pa., assignors, by mesne assignments, to Xaloy Incorporated, New Brunswick, NJ. a corporation of California No Drawing. Filed Nov. 27, 1964, Ser. No. 414,443

I 3 Claims. (Cl. 75-125) ABSTRACT OF THE DISCLOSURE Precipitation hardening stainless steel alloys consisting essentially of from 0.01 to 1.60% carbon, 0.25 to 2.50% manganese, 0.25 to 250% silicon, 10.0 to 30.0% chromium, 0.50 to 10.0% nickel, 0.50 to 10.0% copper, 0.20 to 4.0% boron and the balance iron.

The present invention relates to a precipitation hardening stainless steel alloy having improved hardness and wear and corrosion resistant characteristics, and more particularly to such an alloy desirable for use as a corrosion resistant polished steel for rolls for the plastics and rubber industries, or for other devices requiring hard, wear and corrosion resistant polished surfaces.

In the following specification, all parts and percentages are given by weight, unless otherwise specified.

It is among the objects of the present invention to provide a hard, Wear-resistant stainless steel alloy suitable for use for polished roll surfaces resistant to corrosion by halogen type or other corrosive atmospheres, such as are encountered in the plastics and rubber industries.

Other objects and advantages of the invention will be more fully apparent from a consideration of the following detailed description of preferred embodiment thereof.

The precipitation hardening stainless steel alloy of the present invention comprises the following elements fused together in approximately the proportions stated below.

Ingredient: Weight percent Carbon 0.01-1.60

Manganese 0.25-2.50 Silicon 0.25-2.50

Chromium 100-30.0 Nickel 0.50-10.0 Copper 0.50-10.0 Boron 0.20-4.00

Iron Balance The element boron in this alloy may perform the function that columbium and tantalum perform in the conventional precipitation hardening stainless steels such as 17- 4-PI-I. Alternatively, up to about 1.0% by weight columbium or tantalum may be incorporated in the alloy, if desired. It will be understood that phosphorus and sulfur impurities may also be present in the alloy, in amounts of up to about 0.05%, it being intended that, as used herein, the expression up to includes zero percent thereof.

It has been found that stainless steels having compositions of the indicated ingredients in the proportions specified above possess hardness of from about 45 to 55 Rockwell C, above the range usually found in conventional precipitation hardening stainless steels. Furthermore, the indicated stainless steel of the present invention provides superior wear-resistance as compared with various commercially available materials utilized primarily for roll manufacture such as (1) stainless steels of the types 17-4-PH, HM355, etc.

It is believed that the superior hardness and corrosion characteristics of the novel alloys of the present invention result, at least in part, from the presence of chromiumboride-carbides, which are exceedingly hard and stable, and which prevent migration of chromium in the cast metal thereby preventing low chromium enveloping of grains which, if it occurs, causes loss of corrosion resistance. It will, of course, be understood that the preceding explanation of the factors to which the improved characteristics of the alloy of the present invention may be attributed is illustrative only, and is not intended in a limiting sense.

We have found that optimum wear-resistance, corrosion-resistance and hardness characteristics are provided with the precipitation hardening stainless steel constituted of from about 0.01 to 1.20% carbon, 0.50 to 1.00% manganese, 0.50 to 1.00% silicon, 15 to 18% chromium, 3 to 5% nickel, 3 to 5% copper, 0.50 to 1.25% boron, and the balance essentially iron.

The stainless steel alloys hereof are, as indicated above, preferably employed in the formation of rolls and liners for various devices requiring hard, wear-resistant and corrosion-resistant materials. The linings may, for example, be formed on the interior surfaces of cylindrical ferrous metal shells and the desired devices fabricated therefrom, e.g., as described in US. Patents 2,275,503 and 2,319,657, and copending application Ser. No. 303,313 filed on Aug. 20, 1963, assigned to the assignee of the present invention.

Preferably, wear-resistant linings are manufactured in accordance with the present invention by initially charging a flux composition (to prevent atmospheric oxidation) into the region in which a lining is to be formed, e.g., into the interior of a tubular steel housing. After capping one end and partially capping the other end of the housing, the unit is placed in a furnace containing an inert atmosphere limting oxidation and thereby slag formation, and heated at temperatures of from about 2,000 to 2,400 F. The alloy composition is thereafter charged to the tubular housing, desirably in molten form, through the partially open end thereof. The assembly is subsequently removed from the furnace and spun to centrifugally from the alloy lining. Upon cooling the housing, the molten metal solidifies and bonds metallurgically to the steel housing. Thereafter, the caps are removed from the ends of the housing and the internal and external diameters desired are finished in customary manner.

The following examples illustrate the method of production of the ferrous alloys and wear-resistant liners and rolls comprising such alloys, in accordance with the present invention.

Example 1 Steel containing low proportions of residuals was admixed with chromium, boron, nickel, copper, silicon and manganese and the resulting mixture heated to a temperature above 3000 F. to melt the same. A portion of the melt was analyzed and found to have the following composition.

Ingredient: Weight percent Carbon 1.59

Manganese 0.72 Silicon 1.29 Chromium 16.12 Copper 4.35 Boron 1.21 Nickel 4.08 Iron, balance to The melt was thereafter cast into bars and shot to facilitate later use for the formation of wear-resistant rolls and liners therefrom. Round bars one inch in diameter were cast in carbon molds and flat-type tensile bars 9 inches long Were cast in sand molds.

Tensile tests of the sand castings fracture before yielding at 100,700 p.s.i. ultimate strength.

Example 2 A melt having the following composition was. formed.

Ingredient: Weight percent Carbon 0.885

Manganese 0.31 Silicon 1.28

Chromium 14.91 Copper 4.49 Boron 0.656

Nickel 4.64

Iron Balance The melt was poured into a 5" x 9" x 4" plate with six risers placed adjacent What wasto be the gage section of three tensile bars. X-ray studies indicated that the test sections were relatively free of shrinkage. Two tensile bars thus produced, heat treated at 900 F. in air and then cooled to ambient temperatures, were found to be characterized by moduli of elasticity of 40 10 psi. and fracture strengths before yield of 128,000 p.s.i. A sand casting produced from the melt had the following hardness characteristics:

Surface hardness as cast 32 Surface hardness after heating at 1900 F. for /2 hr. andair cooling 4748 Surface hardness after heating at 900 F. for 1 hr.

and air cooling 51-52 It may thus be seen that, in accordance with the present invention, a precipitation hardening stainless steel alloy having improved hardness, wear-resistance and corrosion resistance may be produced. Since various changes may be made in the specific embodiments of the alloy and its method of manufacture without departing from the scope of the invention it will be understood that the preceding description is intended as illustrative and not in a limiting sense.

We claim:

1. A hard, wear-resistant and corrosion-resistant precipitation hardening stainless steel alloy consisting essentially of the following ingredients in the proportions stated below.

Ingredient: Weight percent Carbon 0.0l-1.20

Manganese 0.501.00 Silicon 0.50-1.00

Chromium 15.0-18.0

Nickel 3.05.0

Copper 3.05.0 Boron 0.50-1.25

Iron Balance.

2. A hard, wear-resistant and corrosion-resistant precipitation hardening stainless steel alloy consisting essentially of the following ingredients in the proportions stated below.

Ingredient: Weight percent Carbon 1.5 9

Manganese 0.72 Silicon l .29

Chromium 16.12

Nickel 4.08

Copper 4.35 Boron 1 .2 1'

Iron Balance 3. A hard, wear-resistant and corrosion-resistant precipitation hardening tainless steel alloy consisting essentially of the following ingredients in the proportions stated below.

Ingredient: Weight percent Carbon 0.885

Manganese 0.31 Silicon 1.28 Chromium 14.91

Nickel 4.64 Copper 4.49 Boron 0.656 Iron Balance References Cited UNITED STATES PATENTS 2,111,278 3/1938 Charlton 128 XR 2,311,878 2/1943 Schlumpf 75-126 XR 2,967,770 1/1961 Hall 75.125 3,275,426 9/1966 Rowady 75-128 XR OTHER REFERENCES Wasmuht, R.: Metals and Alloys, vol. 3, 1932, p. 110, article entitled Iron-Boron. Alloys and 188 Steels Plus Boron.

DAVID L. RECK, Primary Examiner.

P. WEINSTEIN, Assistant Examiner. 

1. A HAND, WEAR-RESISTANT AND CORROSION-RESISTANT PRECIPITATION HARDENING STAINLESS STEEL ALLOY CONSISTING ESSENTIALLY OF THE FOLLOWING INGREDIENTS IN THE PROPORTIONS STATED BELOW. 